Most Americans are sitting ducks for fraud these days after repeated breaches of sensitive data from stores, websites and even a credit-reporting company. Yet few people are doing anything to protect themselves.

Only about 61 million Americans — just over a quarter of all consumers — checked their credit score or credit report in the two weeks immediately following the Equifax data breach, according to a recent CreditCards.com report.

Seventy-one million adults said they hadn't heard anything at all about the data leak even though Equifax's hack affected as many as 145 million people, including personal information such as Social Security numbers, names and birth dates. That number amounts to more than half the U.S. adult population.

Credit awareness rises sharply with income and education, CreditCards.com found: The majority of consumers with annual household incomes of $75,000 or more and a college degree have checked their credit within the past year. The credit monitoring site surveyed more than 1,000 adults in late September.

"It's concerning that an even greater number of Americans remain in the dark regarding this important issue," CreditCards.com senior analyst Matt Schulz said in a statement.

"This cyber-attack was so big, and it contained so much highly sensitive information, that it's going to linger for a long time. Consumers need to keep their guards up for the foreseeable future," he said.

Only 25 percent of Americans have alerts on all of their credit or debit cards, said the survey of 1,000 adults with a credit or debit card. Fewer have paid for a credit monitoring service.

In addition, the majority of adults haven't changed their PIN codes in the last year, which is one of the most effective fraud self-defense measures, according to Brian Karimzad, the vice president of research at LendingTree.

Karimzad cautions consumers to be more vigilant.

"Always assume that your Social Security number is out there and it's being used by fraudsters," he said.